What it is (overview)

A colonoscopy is a diagnostic procedure that allows a gastroenterologist to look directly at the inside lining of your large intestine (colon) and the rectum using a thin, flexible camera called a colonoscope. It is one of the most accurate tests for evaluating intestinal health and is widely used for colorectal screening and for investigating symptoms related to digestive health.

During the exam, the doctor can identify abnormalities such as polyps (small growths), areas of inflammation, bleeding, narrowing (strictures), or suspicious masses that could represent tumors. If needed, the doctor may also take small tissue samples (biopsies) or remove certain polyps during the same procedure. Because early colon cancer often causes no symptoms, colonoscopy is also used as a preventive health assessment to detect and remove precancerous polyps before they turn into cancer.

The phrase “colonoscopy with patient preparation charges” typically means the listed test cost includes not only the procedure itself but also the services related to bowel preparation (patient prep). Preparation is essential because the colon must be clean for the camera to see the lining clearly. Prep commonly includes a short period of dietary changes (often clear liquids) and taking a prescribed laxative solution to empty the bowel. If preparation is incomplete, important findings can be missed and the test may need to be repeated.

What results mean: A “normal” or “negative” colonoscopy means no significant abnormalities were seen (or only minor findings such as small hemorrhoids). An “abnormal” or “positive” result may report polyps, inflammation consistent with inflammatory bowel disease, diverticulosis, bleeding sources, or a mass requiring biopsy. If polyps are found, the report will describe their size, number, and location, and pathology results (if removed) determine whether they are benign, precancerous, or cancerous. Your doctor uses these findings to guide treatment and to recommend when you should have your next colonoscopy.

When & why it's usually done

A colonoscopy is commonly ordered for both screening (looking for disease before symptoms start) and diagnosis (finding the cause of symptoms). It is often considered the gold-standard test for colorectal screening because it can detect and remove polyps in the same session.

Your clinician may recommend colonoscopy if you have symptoms such as:

• Rectal bleeding or blood in the stool
• Ongoing change in bowel habits (new constipation, new diarrhea, or alternating patterns)
• Persistent abdominal pain, cramping, or unexplained bloating
• Unexplained weight loss
• Iron-deficiency anemia or fatigue suspected to be from slow intestinal blood loss
• Positive stool-based screening test (e.g., FIT/FOBT or stool DNA test)

It is also recommended for people at increased risk, including those with:

• A personal history of colon polyps or prior colorectal cancer
• A family history of colorectal cancer or advanced polyps, especially in a first-degree relative (parent, sibling, child)
• Known or suspected inflammatory bowel disease (ulcerative colitis or Crohn’s disease involving the colon)
• Certain hereditary syndromes (such as Lynch syndrome or familial adenomatous polyposis)
• Prior abdominal/pelvic radiation depending on circumstances

Why bowel preparation matters: Successful bowel preparation is a key part of the test. A clean colon improves visibility, increases the chance of finding small polyps, reduces the likelihood of repeat procedures, and can shorten the exam time. Your medical team will provide instructions on diet changes, timing of the prep solution (often “split dosing” the evening before and morning of the test), and medication adjustments (for example, blood thinners or diabetes medicines) when appropriate.

Common diseases related to it

• Colorectal polyps (including adenomas and serrated polyps)
• Colorectal cancer (colon cancer and rectal cancer)
• Inflammatory bowel disease (ulcerative colitis and Crohn’s disease involving the colon)
• Diverticulosis and diverticular bleeding
• Microscopic colitis (usually diagnosed via biopsy when the lining looks normal)
• Ischemic colitis (reduced blood flow causing inflammation/injury)
• Infectious or antibiotic-associated colitis (including C. difficile–associated colitis, when evaluated alongside other tests)
• Angiodysplasia and other causes of lower gastrointestinal bleeding
• Colonic strictures (narrowing due to inflammation, scarring, or tumors)

Health goals where it may help

• Colorectal screening and early detection of colon cancer
• Prevention of colorectal cancer through identification and removal of precancerous polyps
• Evaluation of rectal bleeding, anemia, or unexplained gastrointestinal blood loss
• Assessment of chronic diarrhea, constipation, or persistent changes in bowel habits
• Monitoring and management planning for inflammatory bowel disease (IBD)
• Overall digestive health evaluation and targeted health assessment based on symptoms or risk factors
• Follow-up surveillance after prior polyps, colorectal cancer treatment, or abnormal stool-based screening results